In 1993, right heart catheterization (RHC) was performed 1.2 million times in critically ill patients in the U.S. at a cost exceeding 2.4 billion dollars. It has not been determined, however, whether RHC improves the survival of critically ill patients or enhances long-term recovery from a serious illness. In fact, there is no conclusive evidence of benefit for most indications for this procedure and no clear guidelines for the appropriate use of this technology. Consequently, the use of RHC varies substantially among physicians and hospitals. For practicing clinicians to sue RHC appropriately, they need clarification of its overall effectiveness and identification of patients subgroups who are more likely to either benefit from or be harmed by the procedure. A multidisciplinary research team will use three large databases to determine the: 1) effectiveness of RHC in terms of survival, functional status, quality of life, and satisfaction with care; 2) variation in use of RHC in seriously ill patients; and 3) association of RHC and utilization of resources in the critically ill. To do this, three large observational databases will be used which 1) are designed to allow adjustment for severity of illness, diagnosis, acute physiology and other important patient characteristics, 2) demonstrate large interhospital differences in use of RHC, and 30 are representative of both critically ill patients in general and of the current use of RHC. The three databases include: 1) the Cleveland Health Quality Choice Project (CHQCP) database [35,000 patients/yr, all ICU admission from 40 ICUs at 30 hospitals in the Greater Cleveland area]; 2) the APACHE III database [17,440 patients from a national sample of 40 hospitals with 42 ICUs]; and 3) the SUPPORT database [9,105 seriously ill patients from 5 hospitals with 15 ICUs]. Effectiveness of RHC will be assessed with respect to survival, functional status, quality of life, and patient satisfaction. To adjust for selection bias, the decision to perform RHC will be modeled using all covariates that either influence the clinician's decision to perform RHC or the outcomes of interest. Effectiveness will be estimated by determining the relationship between RHC and patient outcomes after adjusting for the propensity to perform RHC. Variation in the use of RHC among hospitals and units will be described and examined. The association between RHC, length of stay and intensity of nursing care will be examined in all three databases. The SUPPORT database will be used to explore the relationship between RHC and estimates of the cost of care. The results of the current project will be of direct relevance to health policymakers, to purchasers, to purchasers of medical care, to physicians and their patients who seek guidance in the effective use of RHC, and to investigators who wish to refine the indications for use of this common and expensive technology. Evidence about settings in which RHC either is clearly appropriate will lower barriers to performing controlled trials in populations for which clinical indications for RHC appear equivocal.